1. Field of the Invention
This invention relates to a handy air tool.
2. Description of the Related Art
A convectional handy air tool having an air motor or an air piston used as a driving unit for workpieces comprises a grip and a control valve, housed in the grip for controlling the starting and stopping of the driving unit by selectively opening and closing an air supplying duct and an air exhausting duct provided in the grip, and an operating lever pivoted on the grip for operating the control valve. A handy air tool of this kind is disclosed in Japanese Examined Utility Model Registration Application Publication Sho No. 54-42307 (published on Dec. 8, 1979) and Japanese Examined Utility Model Registration Application Publication Sho No. 61-23739 (published on Jul. 16, 1986).
Since, however, the main body of the conventional air tool including the grip is made of cast iron, the valve chamber for the control valve, the transverse hole for slidably receiving the valve rod of the control valve and the air supplying and exhausting ducts cannot be formed in the main body merely by casting but they must be machined accurately, resulting in increased manufacturing cost.
U.S. Pat. No. 4,016,684 discloses an air tool having a lever lock comprising a contact tab provided in the vicinity of the free end of a control-valve operating lever and a thumb contact designed to allow the contact tab to contact the operating lever under the biasing force of a torsion spring. The lock lever is raised by the operator's thumb against the biasing force of the torsion spring to cause the free end of the contact tab to abut against the operating lever. Thus, the operating lever is prevented from approaching the grip such that the air tool does not unexpectedly start.
When the thumb contact is paced in a locked state or an unlocked state, however, it rubs the surface of the tool body and tends to damage the surface. Further, when the lock lever is locked, the contact tab projects significantly from the tool body and may bump nearby articles and break them.
A general grinding-belt type handy air tool has a grinding belt wound on a pair of pulleys and with tension applied by means of a compression coil. During the attachment, detachment or replacement thereof, the grinding belt is loosened. Japanese Examined Utility Model Registration Application Publication Sho No. 48-34080 (published on Oct. 15, 1973) discloses such a grinder in which a hook provided on one end of an engaging lever pivoted to a tension bar is made engaged with a groove formed in the outer peripheral surface of a housing so as to retain a grinding belt in a loosened state, whereby the grinding belt is detached, attached or replaced.
In a grinder having this belt-loosening mechanism, however, the engaging lever projects from the outer peripheral surface of the housing and inhibits the operation of the grinder in narrow places. Further, when shocks are imposed on the grinder, the engaging lever is likely to be deformed and/or damaged.